Isolation, and the acceptance of quarantine and disease control, have kept New Zealand livestock free of the more serious epizootic diseases which still ravage domestic and wild animals in Europe, Asia, and the Americas. Except for the Maori dog and rat introduced in the fourteenth century, there were no land mammals in New Zealand until Captain Cook released pigs, goats, and sheep on his second voyage in 1773. Only the pigs survived. Cook introduced more domestic animals on his third voyage (1777) and, from the end of the eighteenth century, whalers, sealers, missionaries, and the first small groups of settlers imported some few animals. All present species of domestic animal in New Zealand were established during the immigration of the 1840s.
Sheep scab, a serious skin disease due to infestation with the mange mite Psoroptes communis ovis, was recognised in 1849 and a Scab Ordinance was passed. Scab was eradicated by 1880 through rigorous measures including, in the later stages of the campaign, the slaughter of diseased animals. Bovine pleuro-pneumonia appeared in the South Island in 1864. The seriousness of the disease was recognised; it was eradicated by slaughter. Virus swine fever was recorded between 1895 and 1902, but did not become endemic. It has since been successfully excluded, except for two outbreaks in 1932 and 1953 close to the ports of Wellington and Auckland. Both outbreaks, caused by the illegal introduction of virus-infected meat in ships' garbage, were quickly eradicated. Scrapie, a serious disease of sheep of obscure origin, appeared in 1952 in a South Island flock which had imported stud animals, and there was a second outbreak on another property before the disease was eradicated.
In 1876 an Act was passed “to restrict the importation of cattle and other animals into the Colony of New Zealand”; section 2 prohibited the entry of “all cattle, sheep, horses, swine, goats, and other animals … which are likely to propagate any infections of contagious disease amongst men or animals”. Since then the enactments controlling the importation of animals and animal products and stipulating the conditions of their entry have been made progressively more stringent to maintain New Zealand's relative freedom from communicable animal diseases.
Deficiencies of the trace elements cobalt, copper, iodine, or selenium induce widespread natural diseases of animals. There is also a type of copper deficiency associated with an excess of molybdenum and this is more widespread than that arising from a simple deficiency of copper.
Cobalt deficiency or “bush sickness” occurs widely. It is characterised by loss of appetite, wasting, anaemia, failure to thrive (particularly in young animals), and eventual death, unless the deficiency is corrected. It affects mainly sheep and cattle, though it can occur in all ruminant animals and does affect goats and deer. Severe cobalt deficiency is now rare, for the deficient areas are known and are corrected by regular topdressing with cobalt sulphate. Cobalt-deficient areas have been classified as “severe”, “moderate”, or “marginal”. The classification is based on the responses of animals to cobalt and on analyses of animal livers, of pastures, and of some soils for cobalt content. The accompanying map shows the cobalt-deficient areas.
Copper deficiency is of two kinds: (i) an uncomplicated deficiency found on some peat and sandy soils; and (ii) a deficiency of copper, associated with high molybdenum content in the pasture. This occurs on most peat soils, on some pumice soils, and on some marine and river silts. Some of what is now the most highly productive dairying land in New Zealand, the reclaimed swamp lands of the Hauraki Plains and the Waikato, were almost impossible to farm economically before copper deficiency was recognised as the cause of disease. Cattle of all ages and young sheep are affected. Symptoms vary widely, depending on the severity of the deficiency and whether or not it is complicated by excess of molybdenum. Lambs and calves can suffer unthriftiness, retarded growth, ataxia, and bone fragility; and adult cattle become poorly conditioned and anaemic and their coats often lose colour. On peat lands, when there is excess molybdenum in the pasture, the characteristic symptom is a persistent, severe, debilitating scouring whenever there is a flush growth in spring or, to a less extent, in autumn. Copper sulphate mixed with the usual fertilisers is an effective, and widely used, method of control.
Iodine deficiency causing goitre (mainly in newborn animals), most often affects sheep. Goitre is likely to occur in parts of Otago, Westland and Marlborough, large parts of the Canterbury Plains, between Wanganui and Palmerston North, and in places near Waipukurau, Napier, and Gisborne.
Widespread Selenium-responsive diseases are economically important. Experiments and field trials begun in 1958 have demonstrated that selenium can prevent white-muscle disease in lambs, an associated barren-ewe problem, some forms of unthriftiness in lambs and calves, and exudative diathesis in chicks. There is evidence also that Hepatosis dietetica in pigs and paradontal disease of sheep can be controlled by the use of selenium. Live-weight responses in lambs were obtained in areas shown in the accompanying map.
Metabolic diseases cause serious losses both of dairy and of beef cattle during calving and for some time after. Hypocalcaemia, hypomagnesaemia, and acetonaemia, either singly or together, are common in mature cows and can quickly be fatal if treatment is delayed. Hypomagnesaemia, or grass tetany, attacks calves, dry and milk cows, and males. Early treatment gives good control, but relapses take place and there seems to be a district and seasonal variation in response. In beef herds Hypomagnesaemic tetany is assuming more importance and its greater incidence is often associated with improvement both of pastures and of soil fertility.
Hypocalcaemia, or lambing sickness, is common throughout New Zealand; its incidence in individual flocks may be as high as 25 per cent. Pregnancy toxaemia, also common in ewes and associated with stress (for example, multiple pregnancy, starvation over a period, a check in feeding, or unusual disturbance) can, in some seasons and under certain conditions, cause serious losses.
The clostridial infections are a group of diseases, widespread among sheep and fairly common among cattle, which even today cause heavy losses, although cheap, and efficient vaccines are readily available. Clostridial organisms can form spores and remain dormant in the soil for a long time. Blackleg in cattle or blood poisoning in sheep caused by Clostridium Feseri (chauvoei) often follows docking, shearing, dipping, vaccination, assisted lambing, or any other procedure liable to cause trauma. Enterotoxaemia or pulpy kidney, due to infection with C. perfringens (welchii type D), is an important disease of sheep. It is common in forward single lambs on lush pasture or crops, possible associates with heavy infestations of the tapeworm Moniezia expansa. Wound infection with C. septicum is the common cause of navel ill in lambs; infection can also follow, for example, shear cuts, docking wounds, and dehorning. Black disease in sheep is confined to Hawke's Bay and Gisborne, where it is associated with infestations of the liver fluke Fasciola hepatica. The casual organism C. novyi (oedemations) multiples in areas of liver necrosis caused by the migration of immature flukes. Tetanus (C. tetani) may occur in lambs after docking or castration. Though widespread, it is confined to small areas or to individual farms.
Facial eczema a seasonal disease of sheep and cattle, becomes serious whenever the weather favours the growth of the causal fungas Pithomyces chartarum. Stock eating the dead herbage carrying the spores of this fungus suffer severe liver damage, with consequent photosensitivity and damage to parts of the body not protected by wool or hair. The disease is confined to the North Isoand and small areas of the extreme north of the South Island. It has been described in Victoria, Australia.
Important bacterial diseases of cattle are tuberculosis, Johne's disease, brucellosis, mastitis, and leptospirosis. A national scheme for eradicating bovine tuberculosis has been functioning for some years. It began with cattle used for town milk supply and is being extended to all dairy cattle. The tuberculin test and slaughter method are used in areas where compulsory testing is declared. Before eradication began it was estimated that 10 per cent of dairy cattle in the North Island and 2 per cent in the South Island (though very few beef cattle) were affected. The incidence of the disease has been greatly reduced and within five years will probably be negligible.
Johne's disease is of local importance in, especially, Taranaki and Waikato. In confirmed cases the beasts are slaughtered and compensation paid. Vaccination of calves in the first few days of life has proved an effective control and will probably be used extensively when tuberculosis has been eradicated. Brucellosis is well controlled by vaccinating calves and is part of the routine management of over 80 per cent of dairy farmers and an increasing proportion of beef farmers. When a national vaccinated herd is built up it will be possible to eradicate the disease by testing and subsequent slaughter of the animals which react to the test. Antibiotics have reduced the importance of the various forms of mastitis which for so long severely hindered production in many dairy herds. But the resistant types, particularly those caused by staphylococci, remain and cause serious losses in individual herds. Losses due to leptospirosis are uncommon in adult cattle, but many are carriers; and redwater in calves causes marked seasonal losses on many properties.
The main epidemic viral diseases of cattle do not appear in New Zealand, but malignant catarrhal fever, infectious rhinotracheitis, and cow pox are common. Though the acute form of malignant catarrh (a notifiable disease) is uncommon, a mild infectious nasal catarrh (characterised by marked nasal irritation) is widespread. Its incidence within herds varies from 10 to 100 per cent. This disease can greatly lower milk yield. Cow pox is not caused by the vaccinia virus and is a comparatively mild condition of the udder and teats, with a spontaneous recovery in one to three weeks.
Internal parasites of cattle normally affect animals under two years and usually less than one year old. Important nematodes are Osteryagia and Trichostrongylus axei; Haemonchus contortus, Cooperia spp., and Bosicola radiatum are also found, but are seldom significant. Pulmonary helminthiasis in young stock is commonly caused by Dictyocaulus viviparus; infestation with the liver fluke, Fasciola hepatica, is found in Hawke's Bay, Gisborne, Central Otago, and other smaller areas, the intermediate hosts being the freshwater snails, Simlimnea tomentosa and Limnea alfredi. Infestation with the cattle tick, Haemaphysalis bispinosa, is sometimes heavy in scrub and rough grazing in the north of the North Island, but there are no tick-borne diseases. Coccidiosis in calves and trichomoniasis in adult cattle are the only protozoal diseases worth mentioning. Infection with coccidia of the Eimeria species causes many losses in dairy calves between three weeks and six months; Trichomonas foetus, although probably widespread, rarely causes abortion and infertility.
Bacterial diseases of sheep (other than clostridial) are widespread. Foot rot, caused by Fusiformis nodosus in association with Spirochaeta penortha, is a main cause of loss, especially in high-rainfall country in the west and north. Outbreaks are common in wet weather and up to a third of all sheep in a flock may be affected. Less common in distribution and sporadic in its occurrence, foot abscess, due to infection with Spherophorus necrophorus, also causes much severe lameness, though it is less widespread, and occurs only spasmodically. Infection with Brucella ovis associated with epididymitis in rams and abortions late in pregnancy in ewes was formerly common. Preventive vaccination has reduced the importance and incidence of this disease. Caseous lymphadenitis is common in the South Island; less common in the North Island. Although the causal organism, Corynebacterium pseudotuberculosis, seldom affects the general health of the animal, the typical lesions in the lymph nodes prevent the export of diseased carcasses. When hygiene at shearing is neglected as many as 30 per cent of the older sheep in a flock may catch the disease. Contagious ophthalmia (pinkeye), common in flocks in late summer, is due to the organisms Colesiota conjunctivae. Recovery is normally spontaneous after a few weeks, but the complaint may affect half of the animals on a property and interfere with normal husbandry. When flocks are held in close confinement for a day or more there may be outbreaks of salmonellosis. The disease is uncommon, but is found throughout New Zealand. Up to 25 per cent of a flock may be affected, usually fatally. Most cases are associated with Salmonella typhi-murium, but occasionally other types of salmonella are involved. Abortion in ewes caused by infection with Vibrio foetus is common all over the country and may reach a very high incidence within flocks infected for the first time. It shows itself typically as an abortion storm early in the lambing season, which grows less as the main lambing commences. Recovery is normal and a solid immunity results. On some farms in South Canterbury Johne's disease is regularly diagnosed in older sheep and up to 5 per cent a year became clinical cases. Experimental vaccination has given promising results. The disease has not been reported elsewhere. Fleece abnormalities associated with bacterial invasion are widespread, particularly in prolonged wet or humid seasons. Discolouration of wool fleece rot and mycotic dermatitis are regularly diagnosed and lead to the rejection or downgrading of fleece wools.
The virus disease contagious ecthyma or scabby mouth is common in summer and may spread to every animal in a flock. Sheep rapidly lose condition because of difficulty in feeding; thus the disease is especially serious in fattening lambs. Vaccination is widely used on those infected farms which are known.
Internal and external parasites still cause large losses by death and emaciation and entail immense expenditure in prophylaxis and treatment. The primary parasite, Haemonchus contortus, is ubiquitous and causes severe outbreaks of disease in warm wet weather. Common nematodes secondary to poor nutrition are Ostertagia circumcincta, Trichostrongylus axei in the abomasum, and other Trichostrongylus species in the small intestine. Of less general importance, but capable of causing severe losses within flocks, are parasites of the Cooperia, Namatodirus, Strongyoides, Bunnostomum, Trichuris, Chabertia, and Oesophagostomum species. Heavy infestations of tapeworms of the Monezia species are found in lambs and may predispose to enterotoxaemia. Lungworm, Dictyocaulus filaria, is occasionally responsible for severe losses, but is not common.
External parasites are widespread. Annual dipping is required by law. It is an offence to drive lousy sheep or to offer them for sale. Parasites include the body louse, Damalinia ovis, the lice, Linognathus pedalis and L. ovillus, the ked, Melophagus ovinus, and (in the North Island) the tick, Haemophysalis bispinosa. Fly strike is common in summer, the primary blowflies being Lucilia sericata and Calliphora stygia. Scrotal and leg mange from Chorioptes ovis is widespread and the itch mite Psorogates ovis has been confirmed in a few fine-wool flocks in the South Island. The only important protozoal disease of sheep is toxoplasmosis, due to Toxoplasma gondii. This is common in pregnant ewes and is responsible for perinatal deaths of the lambs of up to a third of the ewes in a flock.
The most important infectious disease of pigs is salmonellosis, caused mainly by Salmonella choleraesuis and occasionally by S. typhi-murium. It is found wherever pigs are kept and may affect all members of a herd. Acute, subacute, and chronic forms of the disease are recognised. It is the main cause of pigs' deaths and failure to thrive. Necrotic ulceration of accidental or surgical wounds, caused by a mixed spirochaete and fusiform bacillus infection, is frequent and may affect entire herds. Ulceration is progressive and, if untreated, may lead to death. Localised in the digits it causes footrot and, in the spermatic cord (after castration), scirrhous cord. Mild forms of Inclusion body rhinitis are often found in young pigs and have marked effect on their thrift. The only important internal parasite. Hyostrongylus rubidus is found in all pig-rearing districts and infects pigs of all ages. Ascaris lumbricoides, Stephanurus dentatus, Trichuris trichura, Oesophagostomum dentatum, and Macracantho-rhynchus hirudinaceus are less significant parasites. External mange due to Sarcoptes scabiei, and infestation with the pig louse, Haematopinus suis, are common. Both cause loss of condition.
Few draught horses are now bred or used; thoroughbreds, hunters, hacks, and ponies (with a very few draft horses) are the main horses bred and used in New Zealand. Their diseases are confined to the normal medical and surgical needs of rearing and managing them in a temperate zone. No unusual diseases are recorded.
And so with diseases of dogs and cats. These latter animals can be imported only direct from Britain and from certain districts of Australia.
Cestode infestations of dogs: The following tapeworm infestations of dogs give rise to intermediate stages in domestic animals and in human beings–Echinococcus granulosus, causing hydatidosis in sheep, cattle, pigs, horses, and man, leading to frequent condemnations of sheep and cattle livers and to recurring sickness and death of human beings; Taenia hydatigena, responsible for intermediate infestation of Cysticercus tenuicollis in sheep, cattle, and pigs; Taenia ovis causing cysts in the musculature of sheep, leading to condemnations of carcasses; and Multiceps multiceps, with its intermediate stage, Cenurus cerebralis, in the brains of sheep and cattle. With the passing of the Hydatids Act of 1959 and the formation of the National Hydatids Council, a national eradication scheme has been enforced. The scheme is based on denying dogs access to animal offal and on regular compulsory diagnostic dosing of all dogs. The results have been encouraging. The scheme should lead to the elimination of these parasites.
Veterinary service to the farming industry is provided by the veterinary club system, by private practice, and by the Animal Industry, and Animal Research Divisions of the Department of Agriculture. Commercial organisations also employ a few veterinarians as advisers.
For many years before 1946 some farmer groups (usually the suppliers of a dairy factory) had retained salaried veterinarians. In 1946 the Veterinary Services Act set up a statutory body, the Veterinary Services Council, to promote and encourage an efficient veterinary service and to ensure the training and employment of enough veterinary surgeons. The Council of 13 members comprises representatives of the Government, farmers' veterinary clubs and associations, the New Zealand Dairy Production and Marketing Board, the Meat Producers' Board, the Wool Board, and the New Zealand Veterinary Association. Five of the members are veterinary surgeons. The funds of the Council are derived annually from the three boards represented on the Council, with a Government subsidy equal to the total sum paid by the contributing boards.
With the help of council subsidies as well as a generous bursary scheme for veterinary students, the introduction of overseas graduates, and the establishment of a superannuation scheme for veterinarians, the club system has developed into a movement comprising over 60 clubs or associations. It employs 200 veterinarians. It gives throughout the country an excellent and steadily expanding clinical service. Thus the veterinary club system, pioneered and developed in New Zealand, has provided the farmer with a reliable clinical service and given the veterinarians who serve it a secure employment.
Since the end of the Second World War the number of veterinarians in private practice has increased markedly to about a third of the total in New Zealand. Most private practitioners are engaged principally in the care and treatment of animals other than primary-producing livestock–that is, mainly with thoroughbreds and with small animals. But an increasing number are, however, serving the needs of farmers.
The Animal Industry Division of the Department (employing at present 50 veterinarians) is responsible for controlling infectious diseases of animals, for preventing the entry of exotic diseases and providing for their eradication and for offering an extension service in animal-disease control and husbandry. The Division is organised under a Director who is the chief veterinary officer for the Dominion. There are five administrative districts–Auckland Palmerston North, Christchurch, Hamilton, and Dunedin, each with a Livestock Superintendent who controls a district staff of veterinarians and livestock instructors
The Stock Act of 1908 and its regulations provides for the control and prevention of infectious diseases of stock. Certain dangerous infectious diseases of stock scheduled under the Stock Act are controlled by field officers of the Division. These officers also investigate deaths and outbreaks of disease among farm stock and they work in the field of animal husbandry to increase production and reduce losses. The Division runs the animal quarantine station on Somes Island in Wellington harbour. The prior permission of the Divisional Director is necessary before stock can be imported. The Government controls all meat inspection services. Veterinarians of the Meat Division train, examine, and give technical and administrative direction to the meat inspectors.
The Animal Research Division is organised round its several research stations. Wallaceville Animal Research Station, 20 miles north of Wellington, is the main centre for the investigation of animal diseases. Its sections deal with pathology, bacteriology, parasitology, biochemistry, and apiculture. A diagnostic section examines specimens sent in by veterinary surgeons and livestock instructors and collaborates in the diagnosis, prevention, and treatment of stock ailments.
There is a maximum-security virus-transmission area near the station for diagnostic animal transmission of suspected exotic disease. Ruakura Animal Research Station, about 3 miles from Hamilton in the centre of a densely stocked dairying area, concentrates on the study of problems of animal husbandry, breeding, and nutrition, with particular stress on the interactions of grazing animals and pastures. This station has contributed greatly to present knowledge of these problems both in New Zealand and overseas. A diagnostic centre at Ruakura gives a service similar to that at Wallaceville.
Whatawhata, a hill country property 12 miles from Hamilton, is an out-station of Ruakura developed for the study of hill-farming problems. Manutuke, near Gisborne, is another outstation of Ruakura used mainly for studying field aspects of facial eczema and supplying material for pathological and biochemical studies of this disease. A diagnostic centre for the southern part of the South Island has been established at Taieri, near Dunedin.
by David William Caldwell, M.R.C.V.S., formerly Chief Advisory Officer (Animal Health), Department of Agriculture.